【作者】 喻湘华；

【导师】 卓仁禧；

【作者基本信息】 武汉大学 ， 高分子化学与物理， 2004， 博士

【摘要】 生物可降解高分子材料的酶促合成在近二十年来得到广泛的研究。固定化酶用于合成生物可降解高分子材料处于刚刚起步阶段。固定化酶除了保持自由酶的催化反应特性外,提高了热、pH等条件下的稳定性,降低了对抑制剂的敏感性,易于保存,分离回收容易,可以多次重复使用,对酶的活力降低较少,在合成生物可降解高分子材料领域越来越受到重视。本文从固定化酶的制备方法,固定化酶在工业上的应用,固定化酶发展的新方向以及固定化酶在合成生物可降解材料上的应用进行了简单的综述。 纳米技术是在二十世纪八十年代诞生并崛起的高新科技。纳米技术在合成固定化酶上的应用也是近年来固定化酶发展的一个新方向。以纳米材料为载体,制备的固定化酶有较大的比表面积以及较大的酶负载量,有利于提高催化效率。本文以戊二醛为偶联剂,制备了以纳米二氧化硅(10 nm)为载体的纳米级固定化猪胰脂肪酶IMPPL。并且以IMPPL为催化剂,分别对四种单体---2,2-二甲基-三亚甲基碳酸酯,三亚甲基碳酸酯,丙交酯,1,4-二氧六环-2-酮的开环聚合进行了较为系统的研究。 生物可降解聚碳酸酯是生物医用材料的一个重要组成部分。它具有良好的生物相容性,生物可降解性和物理机械性能。生物可降解聚碳酸酯在手术缝合线,骨固定材料和药物控制释放等领域的研究和应用越来越受到重视。第二,三章以IMPPL催化2,2-二甲基-三亚甲基碳酸酯以及三亚甲基碳酸酯(TMC)的开环聚合,研究了反应条件如催化剂浓度、聚合反应温度和时间对聚合物反应的影响。实验结果表明IMPPL可以有效的催化两种碳酸酯单体的聚合,聚合过程中没有脱二氧化碳现象发生,而且IMPPL可以回收重复使用。对回收的固定化酶的粒径和结构分别进行了了EM和FTIR表征,发现回收的固定化酶中接枝上了聚碳酸酯链,固定化酶粒径发生了较大变化。这些聚碳酸酯链提高了固定化酶在聚合体系中的分散性,同时也阻碍单体与酶的结合,两种因素对其催化活性起着相互制约的作用。第三章着重进行了IMPPL催化聚三亚甲基碳酸酯的酶促热降解研究。更多还原

【Abstract】 Biodegradable polymer has attracted much attention and got rapid development since the past two decades. Among these studies, the application of immobilized enzyme in the preparation of biodegradable polymer is still in the preliminary stage. Immobilized enzyme has shown many advantages such as preservation of catalytic activity of free enzyme, higher stability to reaction temperature and pH, lower sensitivity to inhibitor, higher stability for storage and non-toxic, it is convenient to recover and can be repeatedly use without much loss of its catalytic activity. So it is expected to gain more and more attention and applications in the catalytic preparation of biodegradable polymers.Nanotechnology has developed rapidly since 1980s. The application of nanotechnology the in preparation of immobilized enzymes has been a new route in recent years. By the use of nanometer materials as carriers for the immobilization of enzymes will endowed the immobilized enzymes with higher specific surface area and more enzyme loading and thus to obtain higher catalytic activity. In these studies, porcine pancreas lipase （PPL） immobilized on silica nanoparticles （10 run） was prepared. It was used as catalyst for the ring-opening polymerization of 2, 2-dimethyltrimethylene carbonate （DTC）, trimethylene carbonate （TMC）, D, L-Lactide, L, L-Lactide and 1,4-dioxan-2-one to evaluate its catalytic activity.Biodegradable polycarbonate is one of the most important biomedical materials, which has good biocompatiblity and biodegradablity. It has been extensively used as bioabsorable suture, bone fixing materials and drug controlled-release carriers. In chapter 2 and 3, the ring-opening polymerization of 2, 2-dimethyl-trimethylene carbonate （DTC） and trimethylene carbonate （TMC） catalyzed by IMPPL were explored. Influences of IMPPL concentration, reaction temperature and reaction time on the molecular weight and yield of corresponding polymers were studied. IMPPL exhibited much higher catalytic activity compared with free PPL. The recycling IMPPL showed even higher catalytic activity and higher molecular weight of polycarbonate could be achieved. It was also found that polycarbonates chains were grafted onto the surface of IMPPL. That would both improve the dispersibility and miscibility of the IMPPL in the polymerization system and increase obstruction of the substrates to makecontact with the poly carbonates-grafted silica catalysts. The two factors determined the catalytic activity of the recovered IMPPL. In chapter 3, enzymatic degradation of PTMC was conducted at different temperatures. The experimental data showed that enzymatic degradation would be accelerated at high temperature.Polylactide （PLA） is one kind of biomaterials for pharmaceutical and medical application. In chapter 4, the ring-opening polymerization of D, L-Lactide and L, L-Lactide catalyzed by IMPPL was studied. Influences of different experimental parameters on the molecular weight and yield of polymers were also studied. It was found that in the same reaction condition, the polymer molecular weight and yield of poly （D, L-Lactide） were higher than that of poly （L, L-Lactide）.Poly （1,4-dioxan-2-one） （PDON） is used to make monofilament sutures and knotting and other surgical devices for its good tenacity. It was usually prepared by the ring-opening polymerization of 1, 4-dioxan-2-one （DON）. In chapter 5, the ring-opening polymerization of DON was performed using IMPPL as catalyst. The reaction products were composed of linear PDON and cyclic oligomers. Most of cyclic oligomers were hexamer to octamer. The yield of cyclic oligomers was influenced by reation time, IMPPL concentration and reaction temperature. The molecular weight of linear PDON ranged from 1000 to 4000. It was also found that the ring-opening polymerization of DON catalyzed by IMPPL could take place at room temperature.1, 4-dioxan-2-one （DON） is an important monomer for the preparation of PDON, however the functional derivatives were scarely reported. It was known that the polymer with functional side group will have new physical, mechanical and other properties for new application. In chapter 6 and 7, two derivatives of DON, 6-hydroxymethyl -1,4-dioxan-2-one （HDON） and 6-methyl -1, 4-dioxan-2-one （MDON）, were prepared. Hyperbranched aliphatic polyester, poly （6-hydroxymethyl-1, 4-Dioxan-2-one） （PHDON）, was prepared by ring-opening polymerization of HDON in bulk. The branching degree of obtained polymers was calculated to be about 0.4. This hyperbranched polyester can allow further surface modification and facilitates prodrug attachment. It may find promising application in biomedical field. The ring-openning polymerization of MDON catalyzed by Sn（Oct）2, Al（OⁱBu）₃, Al（OⁱPr）₃, PPL and IMPPL was failed. Perhaps the stability of the monomer was increased due to the methyl substituent at the monomer ring.更多还原